Section 150-431-114
Release 01
Page 44
TABLE 14. HLU-431 A2LB TEST PROCEDURES
Step
Action
1
Send the in-band Arming and NI LPBK code 11000 into the HLU-431, List 1D, for at least five seconds or at
least four repetitions of the 16-bit ESF data link Arming code 1111 1111 0100 1000 (FF48). (Left bit arrives
first.)
2
Monitor the output of the HLU-431, List 1D for the return of the pattern. Return of pattern indicates that either
the HRU-412 has looped up (if the Smart-Jack Loopback option is ENAbled) or an external NI has looped up (if
the Smart-Jack Loopback option is DISabled), and the HLU-431, List 1D and HRU-412 units have been Armed.
Verify that the HLU-431, List 1D display intermittently indicates “Arm” and also “SMJK,” if the HRU-412 is in
loopback. Also verify, if possible, that the Loopback LED of the HRU-412 is flashing (indicating that the HRU-
412 is armed), or, that the Loopback LED lights steadily (indicating that the HRU-412 is both armed and in
loopback).
3
Once armed, the HLU-431, List 1D can be looped back (NLOC in Figure 15) by sending IOR LPBK activation
code 1101 0011 1101 0011 (D3D3) for at least five seconds. The tester observes the following activation
response:
•
Two seconds of AIS (all ones), followed by:
•
Five seconds of returning data pattern, followed by:
•
231 logic errors (including the frame bit) occur in the returned pattern (10 errors if ILR-1 was sent,
200 errors if ILR-20 was sent, and 20 errors if ILR-2 was sent), followed by:
•
Normal looped data.
Note:
This error pattern will repeat every 20 seconds, as long as the IOR loopback pattern is being sent. This
same 20-second repeat scenario also applies to the Time-out Override and Query commands. It also
applies (with the appropriate number of bit errors) to the other ILR commands.
The HLU-431, List 1D is now in Logic Loopback (NLOC of Figure 15). The display on the HLU-431, List 1D
periodically shows “NLOC” and “Arm” (the HLU-431, List 1D is still armed) in addition to the margin displays.
The Loopback Time-out option (which is user settable to “None,” 20, 60, or 120 minutes) determines the
duration of this loopback, unless it is overridden by the Time-out Override command or a loop-down command
is sent. If the Time-out Override code 1101 0101 1101 0110 (D5D6) is received, the “activation sequence,”
described in “3” above, is repeated, and the automatic timed expiration of the loopback is inhibited. If this
Time-out Override is sent, then the only way to loop the HLU-431, List 1D down is to issue the IR LPDN code
1001 0011 1001 0011 (9393) or to issue the NI LPDN and Disarm code 11100. The automatic time-out timer is
restored during subsequent loopback sessions.
4
Upon completion, the tester sends the IOR LPDN code 1001 0011 1001 0011 (9393) to loop down the HLU-431,
List 1D. The unit remains armed, however, as indicated by the “Arm” message on the HLU-431, List 1D and
the flashing of the HRU-412 Loopback LED.
Table continued on next page
